Hi Leonard!  Sir, now I'm more that certain guys far smarter than me will "chime" in with their opinions.  But based upon my ... my experience, I believe you only need three lines: 1. feed, 2. uniflow/vent, 3. overflow.  The uniflow/vent line serves a dual purpose and is ultimately capped off before starting your engine (assuming you are using exhaust pressure into the tank via the overflow tube.  Here is a couple of solid articles you may want to review: http://flyinglines.org/cognitive.uniflow.html  and  https://www.rcuniverse.com/forum/questions-answers-154/3131525-uniflow-fuel-tank-set-up.html

Hope this helps!